The phrase “electric vehicle” herein encompasses hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery-only electric vehicles (BEV), and the like. An electric vehicle has a motor interposed between a traction battery and a drive shaft of the vehicle, wherein the motor is coupled to the vehicle driveline. The motor may use energy from the traction battery to contribute torque to the vehicle wheels for propelling the vehicle.
Many electric vehicles have a low voltage auxiliary battery for providing energy to accessory loads such as circulation fans, heaters, pumps, etc. Advanced battery technology is being considered to augment or replace the auxiliary battery. A concern is that these advanced batteries will not accept a rapid recharge while their battery cells are at low temperatures even though they retain the ability to provide substantial amounts of energy. In start/stop vehicles this may result in a depleted battery after a series of start/stop events or the inability to provide the start/stop function after an extended period of time. One method of overcoming this problem is to cycle energy in and out of the battery in an effort to cause cell heating. However, at low temperatures little energy can be put back into the battery thereby reducing the battery cycling effectiveness.